What is Fracture Grouting?

It is a grouting technique in which a low viscosity cement grout is injected under high pressure. The grout will split open the ground using hydro fracturing and it creates lenses that would penetrate void spaces or fractures. Soils are also displaced using this process. Fracture grouting is commonly used for structures releveling and on stabilizing overlying structures during tunneling.
It is also known as Compensation grouting this method involves the intentionally fracturing of soil or solid rock by grout under pressure. This result to a compact soil and stiffening of rocks. Use this ground improvement practice where other procedures especially permeation grouting is not applicable on actual. Once the procedure of hydro fracture pressure is exceeded fractures open in the soil or rock and instantly broaden by the incursion of the grout. The process results in releveling and stabilize overlying structures.

Fracture Initiation

Soil types differs on the failure mechanism of a fracture. Grouting for cohesive soil and cohesionless soil (non-cohesive soil) are two different agenda in which the cohesion greatly increases the probability of fracturing.
In case of   relatively impermeable cohesive soils, the fluid of the injected grout cannot permeate and a hydraulic fracture will originate in all cases (Mori and Tamura, 1987). Fractures will occur in cohesion less and relatively permeable soils   only   when the injection fluid has   the   right properties (Pater et al.,   2003, Sanders 2007, Gafar and Soga, 2006). A fracture can occur in sand when the grain stress in one direction.
We use a type of this technique to lens grout radially as shown in the detail below to mitigate expansive clays to a certain degree. We create radial lenses close to the surface and grout in stages every six inches. The amount of stages is usually five to six. This technique creates a barrier to stop soil saturation and Portland cement reduces the effect of the mineral smectite that causes the swelling of the clay.

Advantages of Fracture Grouting

  •       Settlement Control
    • The process can be repeated allowing continued control of settlement.
    • Rate gradient control
    • Dynamic regulation of control fluid is concluded.
    • Quick setting grout
    • Economical

Displacement Soil Fracture Grouting

Soil Fracture grouting technique is where the slurry of cement, soil and water is injected on the soil at high pressure to fracture the soil and filled it with a root-like or thin lens shaped zoned of grout in the soil mass. The material will spread all over the grout hole that makes the soil densify and strengthens the ground.

Procedures of Hydraulic Fracturing

The procedure for Fracture grouting is a well stimulation system in which hydraulically pressurized liquid composed of water,sand, and chemical mixture is used to fracture rocks. Pre-split holes are provided for artificial cracks. Grout is forced down the holes or other holes drilled in the same area. Casing are injected to fracture sections to prepared inserted and grouted. A pressurized fluid carrier of prop pant is injected into the opening casing and spread to the fractures. The casing use for injection remains open after fracturing.

Get in touch!

Contact the specialists at Geo Grout Ground Modification Specialist Inc. of Western United States for your Hydro Fracture Grouting project needs. Call us at (650) 241-2400 for complete information on our Hydro Fracture Grouting services or email us at inquiries@gggms.com to discuss your Hydro Fracture Grouting needs today.

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